1. Field of the Invention
This invention relates generally to cargo transporters and more specifically to automatic, self-guiding transporters having electrically driven wheels actuated by a control mechanism which senses the magnetic field around a buried guide wire.
2. Description of the Prior Art
A great variety of types of systems and devices are used to solve the problem of transporting merchandise or other cargo from one location to another. Common examples of such systems include heavy-duty conveyor belts, fork lifts, pallet jacks, tuggers, tractors and tow line systems.
A few of the disadvantages with cargo transport systems in use today include that they are very expensive, are usually not very flexible and often require an operator in attendance. In recent years, the self-guided, automatic transporter has revolutionized to cargo transport field by providing a low cost, highly flexible and operatorless method of transporting cargo between two or more locations.
An example of a self-guided load transporter is found in U.S. Pat. No. 3,563,327 which discloses the invention of D. Mier. Mier's patent teaches an electrically motorized vehicle driven by a pair of wheels, one each located on opposite rear corners of the vehicle, each motor being controlled independently to track a buried, energized wire.
U.S. Pat. No. 3,628,624 discloses the invention of E. Wesener which, briefly, is a trackless carriage with two individually driven lateral traction wheels, the carriage having four sensors disposed in a diamond-shaped array which coact capacitively or inductively with a continuous guide strip on the floor to steer the vehicle along a predetermined path by controlling the transmission of driving torque to the wheels.
A primary consideration, obviously, with self-propelled vehicles is to make them safe. For this purpose, a great many safety bumpers, sensitive to contact with an obstruction, have been provided. Safety bumpers found in the prior art are typically made of flexible metal, usually stainless steel, bands which detect contact with an obstruction by closing an electrical contact when deformed. Impact detecting safety bumpers found in the prior art universally suffer two disadvantages, the first being that they are expensive and complicated to produce, repair and replace and the second being that they in themselves may present a safety hazard by presenting hard or cutting edges to the operator.
Self-guided automatic load transporters found in the prior art further have the disadvantage that they are difficult to load. Typically, the transporters cannot be loaded by standard pallet jacks or forklifts because they do not have sufficient undercarriage clearance to allow for the stabilizing feet of the lift to slide underneath. Therefore, the transporters necessarily must be loaded by hand or by trucks equipped with extendable forks, i.e., reach trucks.
Another difficulty with automatic transporters of the prior art is their inability to climb over low obstructions that may be along their guide path while still maintaining drive wheel traction.